Ban MPs from voting on or influencing anything they have a vested interest in .

MPs with links to private business should not be allowed to promote , vote on or lobby others to benefit their own interests.

The House of Commons already has rules on conflicts of interests, and on the declaration and registration of interests. These rules are set out in the House of Commons Code of Conduct:

http://www.publications.parliament.uk/pa/cm201516/cmcode/1076/1076.pdf

On conflicts of interest, the House has a rule that "MPs shall base their conduct on a consideration of the public interest, avoid conflict between personal interest and the public interest and resolve any conflict between the two, at once, and in favour of the public interest."

You could start a new petition asking for a specific change to be made to the rules.